The study of the initiation and regulation of the growth factor- mediated signal transduction pathways is of crucial importance to our eventual understanding of the mechanisms controlling growth and proliferation. The loss of control of this apparatus is thought to be a hallmark of malignant transformation. Using human T and B lymphocytes as model systems, this laboratory has shown that cellular activation is accompanied by rapid alterations in transmembrane cation fluxes and phosphatidylinositol turnover, leading to increases in cellular Ca2+, Na+ and pH. This work has been expanded to show that the exotoxin of Bordetella pertussis is a mitogen for human T cells that stimulates the same signal transduction pathway activated by stimulation of the T cell antigen receptor complex. We have also begun to characterize a plasma membrane pertussis toxin receptor. Our data indicates that this receptor is identical to a 55kd membrane protein ADP- ribosylated by the cells. The long-term goal of this grant application is to further our understanding of the inter- relationships of growth factor receptors and stimulus-response coupling for the regulation of growth. This grant application proposes to specifically study the interaction of pertussis toxin (PT) with the T lymphocyte cell membrane, isolate its receptor and make monoclonal antibodies to it, and characterize the receptor and its role in PT-stimulated stimulus-response coupling in human T cell lines. Using the human T cell line, Jurkat, PT binding sites will be characterized as to their number per cell and affinity using radio-iodinated PT. Monoclonal antibodies purified PT will be used to isolate the PT receptor. Surface-iodinated T cells will be prepared and PT will be chemically cross-linked to its receptor and purified using affinity chromatography. Monoclonal antibodies will be generated against the purified receptor for use in further structural studies as well as for the production of PT receptor-negative mutant T cells. These mutants will enable us to study the inter-relationships between the PT receptor and the T3-T cell receptor complex in mediating cellular activation. We will also prepare peptide maps of the purified receptor for amino acid sequencing studies and to locate the site of ADP- ribosylation. These studies will afford insights into both primary and secondary mechanisms by which cells transduce extracellular growth factor signals.